A set of planets not too far from Earth is the best place to find aliens outside our solar system, scientists have confirmed.

New observations of the planets orbiting around the Trappist-1 star – which caused a stir when scientists found a whole set of Earth-like worlds circling it last year – show more detailed information than ever about what life could be like on those planets. When the system was found, scientists described it as a "holy grail" discovery.

Scientists suggest that the planets are made mostly of rock, like the Earth. About 5 per cent of their mass is made up of water – far more wet than Earth, which is only 0.02 per cent water.

“No one ever would have expected to find a system like this," said Hannah Wakeford, from Exeter’s Physics and Astronomy department. "They’ve all experienced the same stellar history because they orbit the same star. It’s a goldmine for the characterization of Earth-sized worlds.

“One of these four could be a water world, one could be an exo-Venus, and another could be an exo-Mars. It’s interesting because we have four planets that are at different distances from the star. So we can learn a little bit more about our own diverse solar system, because we’re learning about how the Trappist star has impacted its array of planets.”